1. Field of the Invention
This invention relates generally to a microelectronic assembly such as a smart card that includes an integrated circuit component. More particularly, the present invention relates to apparatuses and methods for forming displays coupled to a flexible card in which the display is configurable and alterable based upon data that is received from a signal that contains at least a single stream of serial data.
2. Description of Related Art
Microelectronic assemblies typically include integrated circuit components attached to substrates. Electrical interconnections are formed that allow communication between the integrated circuit component and the substrate for sending and receiving signals for processing. One type of a microelectronic assembly is a “smart card” assembly.
“Smart card” assemblies are credit card sized assemblies that include an integrated circuit component attached to a substrate. The integrated circuit component may contain information, such as access privileges, account balances, security information, or other like information. Smart card assemblies typically include a plurality of electrical contacts on the surface of the smart card that permit electrical access to information stored in the integrated circuit component for reading or writing such information. A contact smart card has a face that has a cavity for receiving electrical components such as an integrated circuit connected to electrical contacts. The electrical contacts are exposed at the surface of the smart card.
A contactless “smart card” has a substrate that has a face receiving electrical components such as an integrated circuit, an antenna and a metallic lead connected to the antenna. Contactless smart cards allow utilization of the card without having to make physical contact with a mechanical reader head, thereby making the contactless cards faster to use and their functionality more transparent to the user. An antenna is typically disposed within the card to receive a signal transmitted from a base unit and to transmit a signal back to the base unit. In a contactless card, the integrated circuit component is typically embedded in the substrate and is not attached to metal contacts on the surface of the card. In this manner, the position of the integrated circuit component is not based upon a need to be attached to metal contacts exposed at the surface of the card.
A dual interface smart card is a smart card that combines features from both the contact smart card and the contactless smart card. Dual interface smart cards include contact pads and contactless capabilities. The substrate used for contact smart cards, contactless smart cards generally comprise multiple layers that are laminated together. For example, the substrate may have three flexible layers with two protective outer layers. The flexible layers may be comprised of polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polypropylene sulfate (PPS), or polyester (PET).
Displays form a portion of the smart card. Display panels may be comprised of active matrix or passive matrix panels. Active matrix panels and passive matrix panels may be either transmissive or reflective. Transmissive displays include polysilicon thin-film transistor (TFT) displays, and high-resolution polysilicon displays. Reflective displays typically comprise single crystal silicon integrated circuit substrates that have reflective pixels.
Liquid crystals, electroluminescent (EL) materials, organic light emitting diodes (OLEDs), up and downconverting phosphor (U/DCP), electrophoretic (EP) materials, or light emitting diodes (LEDs) may be used in fabricating flat-panel display panels. Each of these is known in the art and is discussed briefly below.
Liquid crystal displays (LCDs) can have an active matrix backplane in which thin-film transistors are co-located with LCD pixels. Flat-panel displays employing LCDs generally include five different components or layers: a White or sequential Red, Green, Blue light source, a first polarizing filter, that is mounted on one side of a circuit panel on which the TFTs are arrayed to form pixels, a filter plate containing at least three primary colors arranged into pixels, and a second polarizing filter. A volume between the circuit panel and the filter plate is filled with a liquid crystal material. This material will rotate the polarized light when an electric field is applied between the circuit panel and a transparent ground electrode affixed to the filter plate or a cover glass. Thus, when a particular pixel of the display is turned on, the liquid crystal material rotates polarized light being transmitted through the material so that it will pass through the second polarizing filter. Some liquid crystal materials, however, require no polarizers. LCDs may also have a passive matrix backplane which is usually two planes of strip electrodes which sandwich the liquid crystal material. However, passive matrices generally provide a lower quality display compared to active matrices. U/DCP and EP displays are formed in a similar fashion except the active medium is different (e.g., upconverting gas, downconverting gas, electrophoretic materials).
EL displays have one or more pixels that are energized by an alternating current (AC) that must be provided to each pixel by row and column interconnects. EL displays generally provide a low brightness output because passive circuitry for exciting pixel phosphors typically operates at a pixel excitation frequency that is low relative to the luminance decay time of the phosphor material. However, an active matrix reduces the interconnect capacitance allowing the use of high frequency AC in order to obtain more efficient electroluminescence in the pixel phosphor. This results in increased brightness in the display.
LED displays are also used in flat-panel displays. LEDs emit light when energized. OLEDs operate like the LEDs except OLEDs use organic material in the formation of the diode.
Regardless of the type of active medium used, displays are generally comprised of at least a substrate and a backplane. A backplane forms an electrical interconnection of the display and comprises electrodes, capacitors, and transistors.
FIG. 1A illustrates a rigid device in which the active matrix display backplane 10 is coupled to a rigid substrate 12. Typically, the active matrix display backplane is also rigid. FIG. 1B shows another rigid display. There, the active matrix display backplane 10 is coupled to a rigid substrate 12 (e.g., glass). Also shown is a plurality of blocks 14. These blocks may be fabricated separately and then deposited into holes on substrate 12 by a process known as fluidic self assembly; an example of this process is described in U.S. Pat. No. 5,545,291, issued to Stephen J. Smith, et al. These blocks may each contain driver circuitry (e.g., MOSFET and capacitor) for driving a pixel electrode. The active matrix backplane includes transparent pixel electrodes and row/column interconnects (not shown) to electrically interconnect the blocks 14. The plurality of blocks 14 is coupled to the active matrix display backplane 10 and the rigid substrate 12. FIG. 1C shows a reflective display 16 coupled to a rigid substrate 12. FIG. 1D shows a reflective display 16 coupled to a rigid substrate 12. A plurality of blocks 14 is coupled to the reflective display 16 and to the rigid substrate 12.
Placing elements, such as pixel drivers, on a rigid substrate is known. Prior techniques can be generally divided into two types: deterministic methods or random methods. Deterministic methods, such as pick and place, use a human or robot arm to pick each element and place it into its corresponding location in a different substrate. Pick and place methods generally place devices one at a time and are generally not applicable to very small or numerous elements such as those needed for large arrays, such as an active matrix liquid crystal display.
Random placement techniques are more effective and result in high yields if the elements to be placed have the right shape. U.S. Pat. No. 5,545,291 describes a method that uses random placement. In this method, microstructures are assembled onto a different substrate through fluid transport. This is sometimes referred to as fluidic self-assembly. Using this technique, various blocks, each containing a functional component, may be fabricated on one substrate and then separated from that substrate and assembled onto a separate rigid substrate through the fluidic self assembly process.
As noted above, FIGS. 1B and 1D illustrate a display substrate 12 with blocks 14 formed in the rigid substrate 12. These blocks 14 may be deposited through an FSA process. In the FSA process, a slurry containing the blocks 14 is deposited over the rigid substrate 12 and the blocks 14 rest in corresponding openings in the substrate 12.
FIG. 2 shows a block 14 and a circuit element (not shown) on the top surface 18 of block 14. Generally, blocks have a trapezoidal cross-section where the top of the block is wider than the bottom of the block.
FIG. 3 shows block 14 in a recessed region of the rigid substrate 12. Between the block and the rigid substrate is an eutetic layer 13. The block has a top surface 18.
FIG. 4 shows a planar side view of a rigid substrate coupled to a rigid display backplane with a plurality of blocks 14 between the display backplane 30 and substrate 12. The plurality of blocks 14 are functionally part of the display backplane 30 and are deposited onto receptor regions of the substrate 12. Each block 14 drives at least one transparent pixel electrode. The pixel is fabricated over a transistor which is fabricated in the block.
FIG. 5 shows a portion of an array in an active matrix display backplane. The control line rows 31 and 32 in this device are coupled to gate electrodes along a row and the control line columns 34 and 35 are coupled to data drivers which supply pixel voltages which are applied to the pixel electrodes. A column line 34 is connected to a source electrode of field effect transistor (FET) 36. Another column line 35 is coupled to a source electrode of FET 37. A row line 32 is coupled to the gates of both FETs 36 and 37. The drain of FET 36 is coupled through capacitor 38 to a transparent pixel electrode along the row 32 formed by FETs 36 and 37, and the drain of FET 37 is coupled through a capacitor to another pixel electrode along the row. In one typical example, the backplane may be formed by depositing blocks, using an FSA technique, into a rigid substrate (e.g., glass); each block contains a FET and a capacitor and is interconnected to other blocks by column and row conductors that are deposited onto the rigid substrate; and, the capacitor is coupled to a pixel electrode by another conductor that is deposited onto the rigid substrate. The active medium (e.g., a liquid crystal) is deposited at least on the pixel electrodes which will optically change the active medium's properties in response to the combined voltages or currents produced by the pixel electrodes. The active medium at a given pixel electrode 42 will appear as a square or dot in the overall checkerboard type matrix of the display. The actual size of the FETs and the pixel electrodes 42 are not now drawn to scale, but are shown schematically for the purposes of illustration. The interconnect between the rows and columns is comprised of flexible and conductive material. For example, the interconnect could be made of conductive polymers, metals (e.g., aluminum, copper, silver, gold, etc.), metal particles, teflon materials with metal or conductive oxides.
There are disadvantages inherent to the related art. Typically, smart cards are assembled using a deterministic method of placing microelectronic structures onto the substrate. This process is time consuming and laborious. Additionally, smart cards are typically manufactured using a batch process which is not efficient.